We are studying the properties of the insulin inhibited transmembrane NADH dehydrogenase of plasma membranes. Plasma membrane is obtained from mouse liver, rat adipocytes, human erythrocytes and pig erythrocytes. The effects of salts, protonophoric uncouplers and ionophores on the dehydrogenase activity in presence and absence of insulin as well as the effect of insulin on NADH induced atebrin fluorescence changes in the membrane will be studied. Ferricyanide reduction by whole cells of yeast (Saccharomyces) and liver will also be studied and correlated with the rate of proton release from the whole cells with and without insulin. Detergents will be tested to extract the NADH ferricyanide reductase from the membrane. The dehydrogenase(s) will then be purified by column chromatography and isoelectric focusing.